/Engine/Plugins/Runtime/MeshModelingToolset/Source/ModelingComponents/Public/Selection/DynamicMeshPolygroupTransformer.h
Start a transform (eg called at beginning of a user interaction with a 3D gizmo). The caller provides the active Selection that is intended to be transformed.
virtual void BeginTransform ( const [UE::Geometry::FGeometrySelection](API\Plugins\DynamicMesh\Selections\FGeometrySelection) & Selection )